The gold enables the metal to receive a beautiful rich purple "patina" or coating when treated with certain pickling solutions, while shibu-ichi possesses a silver-gray tint, which becomes very beautiful under ordinary atmospheric influences. There are three pickling solutions generally in use. They are made up respectively in the following proportions, and are used boiling :

1 "That most widely employed is No. I. When boiled in No. III solution pure copper will turn a brownish red, and shaku-do, which contains gold, becomes purple. Copper containing a small quantity of antimony gives a very different shade to that resulting from the pickling of pure copper. But the copper produced in Japan is often the result of smelting complex ores, and the methods of purification are not so perfectly understood as in the West. The result is that the so-called 'antimony' of the Japanese art metal-workers, which is present in the variety of copper called kuromi, is a complex mixture containing tin, cobalt, and other metals, so that the operator has a varied series of materials at command with which to secure any particular shade. Each particular tint is the result of very small quantities of metallic impurity.

"Another art material termed mokumè, which signifies

1 Roberts-Austen, Jour. Soc. of Arts, 26th October 1888.

wood grain, is very rare. It may be imitated by soldering thin sheets of different metals or alloys together, layer upon layer, as shown in Fig. 30. Then drill conical holes of

varying depth, A, in the mass, or devices in trench-like cuts of V section, B, and hammer the mass until the holes disappear; the holes will thus be replaced by banded circles, and the trenches by banded lines. Prominences as at C may be produced by bumping up the soldered layers from the back with blunt tools. These prominences are filed down until the sheet is flat; the branded alloys then appear on the surface in complicated sections, and a remarkable effect is produced, especially when the colours of the alloys are developed by suitable pickles.

"Oriental art metal-workers often blend metals and alloys of different colours, by pouring them together at a temperature near the solidifying point of the more infusible of the metals and alloys to be associated. In this way, by pouring the comparatively fusible, gray silver-copper alloy on to fused copper, which is just on the point of 'setting,' the metals unite, but do not thoroughly mix, and a mottled alloy is produced."

1 The solder used by Professor Roberts-Austen contained

Some Chinese and Japanese bronzes have an unusually deep bronze colour, and in some cases possess a very beautiful dead-black "patina." The following analyses by H. Morin show the composition:

The peculiar black colour was proved to belong to the substance of the bronze and not to a superficial coating of sulphide. It increases in intensity with the proportion of lead present. The presence of zinc rather impairs the colour.

1 "In imitation of the above bronzes the following alloys were made by Morin :

No. I gave an alloy exceedingly difficult to work, and without giving any superior results as regards colour, furnished castings which were extremely brittle. No. II, on the contrary, gave an alloy exactly resembling Chinese bronze. Its fracture and polish were identical, and when heated in a muffle, it quickly assumed the peculiar dead

1 Compt. rend. tom. lxxviii. p. 811.

black appearance so greatly admired in Chinese specimens. Hitherto it has been found difficult, if not impossible, to obtain this depth of colour with modern art bronzes, since the surface scales off when heated under similar conditions."

Christophle and Bouillet confirm the results of Morin's analyses, but point out that the presence of lead is by no means essential to the production of a fine black "patina." By peculiar oxidation processes they profess to have succeeded in producing brown, orange-yellow, red, and black patina on pure copper. They are said to consist of the production of cuprous-oxide in two molecular states and of copper sulphide.

Two Japanese bronzes, analysed by Kalischer, and having the colour of brass (Ding. pol. J. tom. ccxv. p. 93), contained

Japanese bronzes analysed by Maumené (Compt. rend. tom. lxxx. p. 1009) gave the following results :—

These alloys showed a hard, granular texture, with small cavities on the interior, and sound on the exterior. In the presence of much antimony their colour becomes sensibly violet, and red with the presence of much iron. The specimens were from 5 to 12 millimetres thick. The alloys were probably not made by melting the metals together, but prepared directly from the ores.

WHITE METALS FOR BEARINGS

§ 85. The metals entering into the composition of the various alloys employed for the above purpose are: copper, tin, antimony, lead, and zinc; but seldom more than three of these constituents are used in any one alloy. In machinery running at high speed, or with great pressure, the bearing surfaces are subject to considerable friction, and in many cases the object of the engineer is rather to reduce this friction to the lowest degree, than to provide a bearing which will withstand great pressure without wearing away. A common practice at the present time is to make the foundation of brass or bronze, and line the bearing surface with a renewable lining of comparatively soft white metal. One great advantage of white metal is its low melting point, so that a worn-out bearing can be readily melted out and replaced by a new one. The white metal is generally melted in an ordinary ladle, and when the journal or mandril is wiped dry and chalked, the molten metal is poured in. Care should be exercised not to raise the metal to too high a temperature, as it not only causes the constituent metals to oxidise unequally, but volatile metals escape, and thus the composition is considerably altered. No dross should be allowed to pass into the bearing along with the metal. The journal should also be warm, so as not to chill the metal too suddenly at the wearing surface. White metal bearings are indispensable for certain purposes; as, for instance, where the shaft resting in the bearing does not run smoothly. If